Systems and methods for graphic display of ST-segment deviation

ABSTRACT

Systems and methods are provided for monitoring a patient and graphically representing ST-segment deviations. A receiver acquires, from a plurality of leads, electrocardiogram (ECG) signals that each includes an ST-segment. A processor processes the ECG signals to determine baseline and current ST-segment deviations relative to an isoelectric value. A display module displays a graph that includes a first axis representing ST-segment deviation values and a second axis representing the plurality of leads. At each location along the second axis representing a respective lead, the graph displays a first set of graphic indicia representing the baseline ST-segment deviations and a second set of graphic indicia representing the current ST-segment deviations. In certain embodiments, the graphic indicia are represented by bar graphs. In other embodiments, the graphic indicia are represented by symbols that may be connected by line segments.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.12/372,580, filed Feb. 17, 2009, now U.S. Pat. No. 7,925,337, which isincorporated herein by reference in its entirety.

TECHNICAL FIELD

This disclosure generally relates to cardiac analysis.

SUMMARY

Systems and methods are provided for graphically representing theprogression of ST-segment deviation in one or more electrocardiogram(ECG) signals.

In one embodiment, a receiver acquires, from a plurality of leads,electrocardiogram (ECG) signals that each includes an ST-segment. Aprocessor processes the ECG signals to determine baseline and currentST-segment deviations relative to an isoelectric value. A display moduledisplays a graph that includes a first axis representing ST-segmentdeviation values and a second axis representing the plurality of leads.At each location along the second axis representing a respective lead,the graph displays a first set of graphic indicia representing thebaseline ST-segment deviations and a second set of graphic indiciarepresenting the current ST-segment deviations. In certain embodiments,the graphic indicia are represented by bar graphs. In other embodiments,the graphic indicia are represented by symbols that may be connected byline segments.

Additional aspects and advantages will be apparent from the followingdetailed description of preferred embodiments, which proceeds withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 graphically represents a typical ECG signal of a normal, healthyperson that includes a P wave, a Q wave, an R wave, an S wave, and a Twave;

FIGS. 2A and 2B graphically represent respective ECG signals that differfrom the typical ECG signal shown in FIG. 1;

FIGS. 3A and 3B graphically represent typical user interfaces thatnumerically display ST-segment deviation values for a plurality ofleads;

FIG. 4 graphically illustrates a typical user interface of a patientmonitor displaying baseline and current ECG signals from three differentleads;

FIGS. 5A and 5B graphically illustrate respective user interfacesdisplaying bar graphs to represent ST-segment deviations for a selectedplurality of leads according to certain embodiments;

FIG. 6 graphically illustrates a user interface in which a differencebetween a baseline ST-segment deviation and a current ST-segmentdeviation changes sign according to one embodiment;

FIGS. 7A, 7B, 7C, and 7D graphically illustrate sloped bar graphs thatprovide indications of ST-segment deviation trends over time accordingto certain embodiment;

FIGS. 8A and 8B graphically illustrate respective user interfacesdisplaying threshold lines relative to bar graphs that represent overallST-segment deviations according to certain embodiments;

FIGS. 9A and 9B graphically illustrate respective user interfacesdisplaying threshold lines relative to bar graphs that represent onlyrelative ST-segment deviations according to certain embodiments;

FIG. 10 graphically illustrates a user interface displaying a first axisalong which bar graphs for limb leads are displayed and a second axisalong with bar graphs for precordial leads are displayed according toone embodiment;

FIGS. 11 and 12 graphically illustrate respective user interfaces fordisplaying plots of ST-segment deviation values according to certainembodiments;

FIGS. 13A and 13B graphically illustrate respective user interfacesdisplaying highlighting between a first line graph representing baselineST-segment deviations and a second line graph representing currentST-segment deviations according to certain embodiments; and

FIG. 14 is a simplified block diagram of a system 1400 for monitoringST-segment deviation according to one embodiment.

DETAILED DESCRIPTION

Electrical waves cause the heart muscle to pump. These waves passthrough the body and may be measured using electrodes attached to apatient's skin. Electrodes on different sides of the heart measure theactivity of different parts of the heart muscle. An electrocardiogram(ECG) displays voltages between pairs of electrodes (leads) fromdifferent directions. Thus, an ECG may be used to display an overallrhythm of the heart and weaknesses in different parts of the heartmuscle.

ECGs are used to measure and diagnose abnormal rhythms of the heart,including abnormal rhythms caused by damage to the conductive tissuethat carries electrical signals. The ECG may be measured using variouslead systems. Generally, the ECG is obtained by using a standard 12-leadarrangement, but it can be obtained by using other lead systemsincluding, for example, a 5-lead system or a 3-lead system.

When patients have myocardial ischemia or injury, an ST portion(discussed below) of the ECG signal in affected leads may deviate froman isoelectric line. The affected leads may indicate an ST elevationfrom the isoelectric line, and the reciprocal leads may indicate STdepression from the isoelectric line. Cardiologists quantify ST-segmentdeviation in the affected leads to identify which patients with STelevation myocardial infarctions (STEMI) are at greater risk and mayneed more aggressive intervention.

Patient monitors typically display ST-segment deviation values inmillimeters where 100 μV=1 mm. Looking at a set of numerical values,however, may not be the easiest or quickest way to integrate theinformation from multiple leads and determine whether an ischemic stateis getting worse or improving. Thus, according to certain embodimentsdisclosed herein, ST-segment deviations corresponding to monitored leadsare graphically displayed so that a user (e.g., a clinician) can get amore complete picture of changes in a patient's condition over time.Because limb leads and precordial leads represent different planes,ST-segment deviations for the two sets of vectors are presented in someembodiments on two separate graphs.

In certain embodiments disclosed herein, systems and methods areprovided for monitoring and graphically displaying ST-segment deviationsto a user in a way that allows for quick and simple evaluation of trendsin the patient's condition. Bar graphs, plots, or line graphs may beused to illustrate baseline and current ST-segment deviation values.Highlighting may also be used to distinguish between the baseline andcurrent ST-segment deviation values and/or to emphasize changes in thedifference between the baseline and current ST-segment deviation values.

The embodiments of the disclosure will be best understood by referenceto the drawings, wherein like elements are designated by like numeralsthroughout. In the following description, numerous specific details areprovided for a thorough understanding of the embodiments describedherein. However, those of skill in the art will recognize that one ormore of the specific details may be omitted, or other methods,components, or materials may be used. In some cases, operations are notshown or described in detail.

Furthermore, the described features, operations, or characteristics maybe combined in any suitable manner in one or more embodiments. It willalso be readily understood that the order of the steps or actions of themethods described in connection with the embodiments disclosed may bechanged as would be apparent to those skilled in the art. Thus, anyorder in the drawings or Detailed Description is for illustrativepurposes only and is not meant to imply a required order, unlessspecified to require an order.

Embodiments may include various steps, which may be embodied inmachine-executable instructions to be executed by a general-purpose orspecial-purpose computer (or other electronic device). Alternatively,the steps may be performed by hardware components that include specificlogic for performing the steps or by a combination of hardware,software, and/or firmware.

Embodiments may also be provided as a computer program product includinga machine-readable medium having stored thereon instructions that may beused to program a computer (or other electronic device) to performprocesses described herein. The machine-readable medium may include, butis not limited to, hard drives, floppy diskettes, optical disks,CD-ROMs, DVD-ROMs, ROMs, RAMs, EPROMs, EEPROMs, magnetic or opticalcards, solid-state memory devices, or other types ofmedia/computer-readable medium suitable for storing electronicinstructions.

FIG. 1 graphically represents one beat of a typical ECG signal 100 of anormal, healthy person that includes a P wave, a Q wave, an R wave, an Swave, and a T wave. The P wave indicates atrial depolarization. Theinitial portion of the P wave is largely a reflection of right atrialdepolarization and the terminal portion is largely a reflection of leftatrial depolarization. When visible, the Q wave is any initial downwarddeflection after the P wave. The typical Q wave represents septaldepolarization. The R wave is the first upward deflection after the Pwave and represents early ventricular depolarization. The S wave is thefirst negative deflection after the R wave and represents lateventricular depolarization. The T wave is normally upright, somewhatrounded and slightly asymmetric. The T wave represents repolarization ofthe ventricles. A QRS complex 110 begins at the onset of the Q wave andends at the endpoint of the S wave. The QRS complex 110 represents theduration of ventricular depolarization.

Generally, little or no electrical activity is visible along anisoelectric line 112 during a PR-segment 114 and an ST-segment 116 ofthe ECG signal 100. The PR-segment 114 begins at an endpoint of the Pwave and ends at the onset of the QRS complex 110. During the PR-segment114, an electrical impulse travels from the AV node through theconducting tissue (bundle branches and Purkinje fibers) towards theventricles. Thus, the PR-segment 114 corresponds to the time it takesfor the electrical impulse to reach the ventricles from the AV node.Most of the delay in the PR-segment 114 occurs in the AV node. TheST-segment 116 begins at the endpoint of the S wave and ends at theonset of the T wave. During the ST-segment 116, the atrial cells arerelaxed and the ventricles are contracted so that electrical activitymay not be visible. In other words, as indicated above, the ST-segment116 is normally isoelectric.

FIGS. 2A and 2B graphically represent one beat of respective ECG signals210, 212 that differ from the “typical” ECG signal 100. As shown inFIGS. 2A and 2B, the ST-segment 116 may experience elevation (FIG. 2A)or depression (FIG. 2B) from the isoelectric line 112 in a verticaldirection. ST-segment elevation or depression may occur, for example,with cardiac injury, ventricular aneurysms, Prinzmetals angina,pericarditis, myocardial ischemia, or other diseases. An artisan willrecognize from the disclosure herein that ST elevation shown in FIG. 2Aand the ST depression shown in FIG. 2B may occur in the same patient asdetected through different leads.

FIGS. 2A and 2B also illustrate locations of respective J-points 214 andST-points 216. The J-point 214 is a junction between the QRS complex 110and the ST-segment 116. The ST-point 216 is a selected time durationfrom the J-point 214 and the amplitude of the ST-segment is measured atthis point. For example, traditional ST-segment measurements may be madeat approximately 1/16×R-R interval post J-point, where the R-R intervalis the heart beat interval or distance between a selected point on oneECG beat to the corresponding point on the succeeding beat. Thiscorresponds, for example, to a 60 msec post J-point time at a heart rateof approximately 60 beats per minute. Generally, the ST-point 216 isselected to be between approximately 40 msec and approximately 80 msecafter the J-point.

As shown in FIGS. 2A and 2B, the ST-segment deviation 218 is thevertical distance between the isoelectric line 112 and the ST-point 216.The voltage (vertical distance) between the isoelectric line 112 and theST-point 216 is typically measured in microvolts. Generally, however,ECG signals are often recorded on a strip chart recorder (not shown)with a scale of 1 cm/mV and ST-segments are conventionally read inmillimeters where 1 mm is equivalent to 0.1 mV.

ST-segment deviation values in millimeters are typically displayed oneither an ECG section (tile) or on a separate ST parameter tile on apatient monitor. For example, FIG. 3A graphically represents a userinterface 300 of a patient monitor (not shown) that displays ST-segmentdeviation values (in millimeters) for a plurality of leads. Looking atthe user interface 300 of numerical values, however, is not the easiestor quickest way to integrate the information from multiple leads (e.g.,leads I, II, III, aVR, aVL, aVF, V1, V2, V3, V4, V5, and V6) todetermine whether or not ischemia is present and where such ischemia maybe located.

As shown in FIG. 3A, such a display may be very cluttered, which makesit difficult to quickly glean important or relevant information from theuser interface 300. Further, the typical user interface 300 of numericinformation corresponding to current ST-segment deviation valuesprovides no information to help a user determine whether the ischemia isimproving or getting worse because it does not display any initial orbaseline ST-segment deviation values. As shown in FIG. 3B, providingsuch information would make the user interface 300 shown in FIG. 3 evenmore cluttered because it would display 24 numerical values instead of12 numerical values. In FIG. 3B, the user interface 300 displays theinitial ST-segment deviation (shown in parenthesis) as well as thecurrent ST-segment deviation.

ST-segment deviation may also be illustrated by overlaying a baselineECG signal with a current ECG signal. For example, FIG. 4 graphicallyillustrates a user interface 400 of a patient monitor (not shown)displaying baseline and current ECG signals from three different leads(e.g., leads II, aVR, and V1). In the example shown in FIG. 4, thebaseline ECG signals are shown in dashed lines and the current ECGsignals are shown in solid lines. A user may manually determine theST-segment deviations of the three leads by comparing the baseline ECGsignals with the current ECG signals, or the ECG signals may beautomatically calculated and displayed in a separate tile, such as theuser interface 300 shown in FIG. 3. A disadvantage of overlappingbaseline and current ECG signals, as shown in FIG. 4, is that suchdisplays are typically small and cluttered. Thus, such displaystypically include ECG waveforms from only a few leads, are not combinedwith numerical data, and provide little or no trend information (e.g.,they do not indicate whether the ST-segment deviation is currentlyincreasing or decreasing.

Thus, the embodiments disclosed herein graphically represent ST-segmentdeviation to allow a user to quickly evaluate a patient's currentcondition as well as trends in the patient's condition. A graphicalmethod according to one embodiment displays both the initially learnedvalues (e.g., baseline values) and current ST-segment deviation valuesfor all, or a selected subset, of the leads. In certain embodiments,different colors are used to indicate the baseline values and thecurrent values. In addition, or in other embodiments, informationcorresponding to limb leads is displayed in a first window andinformation corresponding to precordial leads is displayed in a secondwindow.

FIGS. 5A and 5B graphically illustrate respective user interfaces 510,512 displaying bar graphs to represent ST-segment deviations for aselected plurality of leads according to certain embodiments. Asdiscussed below, using a series of bar graphs allows ST-segmentdeviation data for multiple leads to be displayed together, whileproviding that data for each lead is represented as a separate graphicalobject. Each user interface 510, 512 may be displayed, for example, in adifferent window or portion of a patient monitor. Each user interface510, 512 includes a first linear axis 514 representing ST-segmentdeviation values (in millimeters) and a second linear axis 516representing the respective plurality of leads. In this example, thesecond linear axis 516 intersects the first linear axis 514 at 0.0 mm.Thus, the second linear axis 516 is displayed so as to correspond to theisoelectric value.

In the example embodiment shown in FIG. 5A, the user interface 510displays the names of limb leads (e.g., I, II, III, aVR, aVL, and aVF)at respective locations along the second linear axis 516. In the exampleembodiment shown in FIG. 5B, the user interface 512 displays the namesof precordial leads (e.g., V1, V2, V3, V4, V5, and V6) at respectivelocations along the second linear axis 516. In certain embodiments, auser may select how many and which particular leads are displayed alongthe second linear axis 516. In addition, or in other embodiments, theuser may selectively combine limb leads and precordial leads on the sameaxis 516.

At each respective lead location along the second linear axis 516, afirst bar graph (illustrated without highlighting) represents a baselineST-segment deviation for the corresponding lead. The respective baselineST-segment deviation values may be acquired, for example, when the leadsare initially attached to the patient, after treatment is provided tothe patient (e.g., upon administering a thrombolytic), or at anyuser-selected time. Because ST-segment deviation is measured relative tothe isoelectric line, each of the first bar graphs extends from thesecond linear axis 516 (at 0.0 mm) to its respective baseline ST-segmentdeviation value, which is indicated along the first linear axis 514.

Further, at each respective lead location along the second linear axis516, a second bar graph (illustrated with highlighting) represents acurrent ST-segment deviation for the corresponding lead. The respectivecurrent ST-segment deviation values may be updated periodically asadditional data is acquired through the leads attached to the patient.Generally, users may be interested in the difference between thebaseline and current ST-segment deviations. Thus, as shown in FIGS. 5Aand 5B, each of the second bar graphs begins at its respective baselinevalue (e.g., the end of the first bar graph for the corresponding lead)and ends at its current ST-segment deviation value, as indicated alongthe first linear axis 514. Thus, the difference between baseline andcurrent ST-segment deviations for a plurality of leads may be quicklyand easily evaluated by the user.

As shown in FIGS. 5A and 5B, in certain embodiments, the second bargraph at each location along the second linear axis 516 may behighlighted to clearly indicate the difference between the baseline andcurrent ST-segment deviations. In other words, the height of each of thehighlighted bars represents a relative change in ST-segment deviationfor the respective lead. Thus, for example, by observing changes in thehighlighted areas of the user interfaces 510, 512, the user can quicklygauge whether ST-segment deviation is increasing or decreasing withouttranslating a series of numbers.

For illustrative purposes, the examples provided herein show thehighlighting as hatching (e.g., a series of slanted parallel lines).However, an artisan will recognize from the disclosure herein that anytype of highlighting may be used such as shading, coloring, or the useof other graphical elements. Further, an artisan will recognize from thedisclosure herein that two or more of the second bar graphs may havedifferent highlights. For example, the second bar graph illustrating thecurrent ST-segment deviation for the lead aVR may be a first color andthe second bar graph illustrating the current ST-segment deviation forthe lead aVL may be a second color. In addition, or in otherembodiments, the first bar graph at each location along the secondlinear axis 516 may also be highlighted. For example, the first bargraph illustrating the baseline ST-segment deviation for the lead V2 maybe a first color and the second bar graph illustrating the currentST-segment deviation for the lead V2 may be a second color.

In certain embodiments, the user interfaces 510, 512 also displaynumerical values associated with the first bar graphs, the second bargraphs, and/or the difference between the respective first bar graphsand the second bar graphs. In the embodiments shown in FIGS. 5A and 5B,the difference between each lead's baseline ST-segment deviation valueand current ST-segment deviation value is displayed. For example, thenumerical value “0.8” is displayed in the second bar graph correspondingto the lead I. As shown in FIG. 5A, because the baseline ST-segmentdeviation value is 0.6 mm and the current ST-segment deviation value is1.4 mm, the displayed text “0.8” is an indication of the differencebetween the baseline and the current values for the lead I. An artisanwill recognize from the disclosure herein that the display of thenumerical values is not limited to a location within the area of thesecond bar graph. For example, such numerical values may be displayedwithin the area of the first bar graph, at the boundary between thefirst bar graph and the second bar graph, or proximate the area of thefirst bar graph or the second bar graph.

As shown in FIGS. 5A and 5B, in certain embodiments, the width (in thedirection of the second linear axis) of the second bar graph is narrowerthan the width of the first bar graph corresponding to the same lead.This further helps to clearly separate the current ST-segment deviationfrom the baseline ST-segment deviation for a particular lead. This isalso useful, for example, when an ST-segment deviation value changesdirection as compared to its baseline value.

For example, FIG. 6 graphically illustrates a user interface 600 inwhich a difference between a baseline ST-segment deviation and a currentST-segment deviation changes sign according to one embodiment. In FIG.6, the current ST-segment deviations for the leads V1, V2, V5, and V6have increased as compared to their respective baseline ST-segmentdeviations. However, the current ST-segment deviations for the leads V3and V4 have decreased as compared to their respective baselineST-segment deviations.

Accordingly, the second bar graph corresponding to the lead V3 extendsfrom the baseline value back into the first bar graph for the lead V3.In this embodiment, the numerical value “−0.2” is also displayed toindicate that the current ST-segment deviation has decreased by −0.2 mmas compared to the baseline ST-segment deviation. Similarly, the secondbar graph corresponding to the lead V4 extends from its baselineST-segment deviation value back into the first bar graph for the lead V4and the numerical value “−0.7” is displayed to indicate the differencebetween the baseline and current values. Because the second bar graphsare narrower than the first bar graphs for the leads V3 and V4, theheights (e.g., baseline values) of the first bar graphs are clearlyvisible and the differences between the respective baseline and currentvalues are clearly depicted by the highlighted second bar graphs.

In certain embodiments, at least a portion of the second bar graphs areangled or sloped toward or from their respective current ST-segmentdeviation values so as to indicate a trend in the ST-segment deviationover time for the respective leads. For example, FIGS. 7A, 7B, 7C, and7D graphically illustrate sloped bar graphs that provide indications ofST-segment deviation trends over time according to certain embodiment.As discussed above, the height of a first bar graph 710 represents abaseline ST-segment deviation value for a particular lead. In FIG. 7A,the height of a second bar graph 712 represents a current change in theST-segment deviation value for the particular lead. As shown in FIG. 7A,the top of the second bar graph 712 slopes upward to the right, whichcorresponds to a direction of increasing time, until it ends at thecurrent ST-segment deviation value. Thus, the upward slope of the secondbar graph 712 indicates that the change in ST-segment deviation iscurrently trending upward. Similarly, in FIG. 7B, the top of a secondbar graph 714 slopes downward with time to indicate that the change inST-segment deviation is currently trending downward.

In FIGS. 7C and 7D, the respective slopes are unrelated to a directionof increasing time. Rather, the slopes in these embodiments point in thedirection of changing ST-segment deviation. In FIG. 7C, the top of asecond bar graph 716 slopes both upward and downward to form an upwardpointing peak at the current ST-segment deviation value. The upwardpointing peak graphically indicates that the ST-segment deviation iscurrently trending upward. In FIG. 7D, the top of a second bar graph 718slopes both downward (from the current ST-segment deviation value) andupward (to the current ST-segment deviation value) to form a downwardpointing valley. The downward pointing valley indicates that theST-segment deviation is currently trending downward. Artisans willrecognize from the disclosure herein that other indicia may be providedon or near the second bar graphs to indicate current ST-segmentdeviation trends. For example, arrows or text such as “up” or “down” maybe displayed to indicate the current trends.

In certain embodiments, one or more threshold lines are displayedrelative to the bar graphs to indicate threshold levels at which STalarms are set. For example, FIGS. 8A and 8B graphically illustraterespective user interfaces 810, 812 displaying threshold lines 812, 814,816, 818 relative to bar graphs that represent overall ST-segmentdeviations according to certain embodiments. In this example, upperthreshold lines 812, 816 are set at 2.0 mm and lower threshold lines areset at −2.0 mm. As shown in FIG. 8A, the current ST-segment deviationvalue of the lead II has surpassed the upper threshold line 812. Asshown in FIG. 8B, the current ST-segment deviation value of the lead V5has surpassed the upper threshold line 816.

In certain embodiments, the highlighting of the second bar graph changeswhen it reaches one of the threshold lines 812, 814, 816, 818. Forexample, the second bar graph for the lead II in FIG. 8A may changecolors (e.g., from green to blue) when the current ST-segment deviationfirst reaches 2.0 mm. Other responses to reaching an ST alarm limitinclude, for example, causing the second bar graph to flash, sounding anaudible alarm, providing an alarm signal to a remote device or system,or combinations of the foregoing.

In certain embodiments, a user may independently set the respectivethreshold lines 812, 814, 816, 818 at any value. For example, the usermay set the limb (FIG. 8A) upper threshold line 812 to 2.5 mm and lowerthreshold line 814 to −3.0 mm, and the precordial (FIG. 8B) upperthreshold line 816 to 1.5 mm and the lower threshold line 818 to −1.0mm. In other embodiments, the user may selectively set threshold linesfor each lead independently. In FIG. 8A, for example, the user may set afirst upper threshold line (not shown) for the lead II to 2.5 mm and asecond upper threshold line (not shown) for limb III to 1.5 mm. Asanother example, in some embodiments, a user may set a single thresholdvalue, such as 1.0 mm, that is automatically applied to the relativechanges in each lead. In such embodiments, the user interface displays adifferent threshold line for each lead that is 1.0 mm (in this example)above or below the baseline ST-segment deviation value for that lead.If, for example, the baseline ST-segment value for a particular lead is1.1 mm, then the user interface would display a threshold line of 2.1 mmfor that lead. Similarly, if the baseline ST-segment value for aparticular lead is −0.5 mm, then the user interface would display athreshold line of −1.5 mm for that lead. An artisan will recognize fromthe disclosure herein that the threshold values disclosed are providedby way of example only, and not by way of limitation.

Because ST-segment measurements are generally represented as relativechanges with respect to baseline values, and because ST alarms aregenerally set based on such relative changes, some embodiments displaythreshold lines with respect to only relative changes in ST-segmentdeviation. For example, FIGS. 9A and 9B graphically illustraterespective user interfaces 910, 912 displaying threshold lines 912, 914,916, 918 relative to bar graphs that represent only relative ST-segmentdeviations according to certain embodiments. In this example, upperthreshold lines 912, 916 are set at 1.0 mm and lower threshold lines914, 918 are set at −1.0 mm.

As compared to the embodiments discussed above, the first bar graphsrepresenting the baseline ST-segment deviations are not shown in theembodiments of FIGS. 9A and 9B. Rather, only bar graphs are shown thatrepresent differences between the baseline and current ST-segmentdeviation values. Accordingly, the 0.0 mm value along the first linearaxis 514 represents zero change from each respective lead's baselineST-segment deviation value. Thus, each displayed bar graph begins at 0.0mm and ends at the difference between its respective baseline andcurrent ST-segment deviation values.

While certain embodiments discussed above display graphs for certainleads in a first window (or first portion of a window) and graphs forother leads in a second window (or second portion of a window), thedisclosure herein is not so limited. For example, bar graphs for bothlimb leads and precordial leads may be displayed in the same window oralong the same set of axes 514, 516. Further, in certain embodiments,both axes 514, 516 need not be displayed. For example, FIG. 10graphically illustrates a user interface 1000 displaying a first axis1010 along which bar graphs for limb leads are displayed and a secondaxis 1012 along with bar graphs for precordial leads are displayedaccording to one embodiment. In this example, the axes 1010, 1012 areparallel to each other, but slanted at an angle so as to fit all of thebar graphs within a predetermined space on a single display device.

In certain embodiments, rather than displaying bar graphs, other graphicindicia are displayed to represent ST-segment deviation. For example,FIG. 11 graphically illustrates a user interface 1100 for displaying aplot of ST-segment deviation values according to one embodiment. In thisexample, baseline ST-segment deviations are represented by darkenedsquares 1110 that are plotted relative to their respective values (e.g.,between 3.0 mm and −3.0 mm) shown along a first axis 514 and theirrespective leads (e.g., limb leads I, II, III, aVR, aVL, and aVF) shownalong a second axis 516. Similarly, current ST-segment deviations arerepresented in this example by (undarkened) squares 1112 that areplotted relative to their respective values shown along the first axis514 and their respective leads shown along the second axis 516. Ofcourse, any graphic symbol may be used to represent the ST-segmentdeviation values such as squares, circles, diamonds, stars, asterisks,or any other shapes. Further, as discussed above, highlighting such asdifferent shadings or colors may be used to distinguish between thebaseline and current ST-segment deviation values.

Further, as shown in FIG. 12, the graphic indicia may be connected byline segments 1210, 1212. In the example of FIG. 12, the darkenedsquares 1110 representing baseline ST-segment deviations are connectedby solid line segments 1210 and the squares 1112 representing currentST-segment deviations are connected by dashed line segments 1212. Inaddition, or in other embodiments, the line segments 1210, 1212 may bedifferent colors to distinguish between baseline and current ST-segmentdeviations. Connecting the data points with the respective line segments1210, 1212 helps the user to quickly interpret the data. For example,over time, the user can visually observe the area between the two curvescreated by the two sets of line segments 1210, 1212. An increasing areabetween the two curves indicates, for example, a worsening ischemia.

In certain embodiments, the area between the two curves may behighlighted. For example, FIGS. 13A and 13B graphically illustraterespective user interfaces 1310, 1312 displaying highlighting between afirst line graph 1314 representing baseline ST-segment deviations and asecond line graph 1316 representing current ST-segment deviationsaccording to certain embodiments. FIG. 13A represents limb leads (e.g.,I, II, III, aVR, aVL, and aVF) and FIG. 13B represents precordial leads(e.g., V1, V2, V3, V4, V5, and V6). In this example, the squares 1110,1112 shown in FIGS. 11 and 12 are not displayed. Rather, the graphicindicia are simply the line segments that extend between respectivebaseline and current ST-segment deviation values.

For illustrative purposes, the highlighting in FIGS. 13A and 13B isrepresented by shading with small dots. In other embodiments, asdiscussed above, the highlighting may include other types of shading,hatching, coloring, or combinations of the foregoing. Further, thehighlighting in certain embodiments may change when an ST alarmcondition is met. The alarm condition may be met, as discussed above,when a current ST-segment deviation value (or difference between acurrent value and a baseline value) reaches a predetermined threshold.

FIG. 14 is a simplified block diagram of a system 1400 for monitoringST-segment deviation according to one embodiment. The system 1400includes a plurality of leads 1410 electrically connected to a receivercomponent 1412 that is in communication with a processor 1413, a memorydevice 1414, a display device 1416, an audio component 1418, and aninterface component 1420. The leads 1410 include wires and electrodesconfigured to attach to a patient (not shown) to detect ECG signals. Thereceiver 1412 may include, for example, an amplification component 1422to amplify the ECG signals detected by the leads 1410, a filteringcomponent 1424 to eliminate undesirable noise from the ECG signals, andan analog-to-digital (ND) converter 1426 to provide converted ECGsignals through a system bus 1428 to the processor 1413.

The processor 1413 may include a special purpose processor configured toperform the processes described herein. In another embodiment, theprocessor 1413 is a general purpose processor configured to executecomputer executable instructions (e.g., stored in computer-readablemedium such as the memory device 1414) to perform the processesdescribed herein. In addition, or in other embodiments, the processor1413 may be connected to a host computer 1430 having a display device1432. The host computer 1430 may include computer executableinstructions for performing the processes described herein. The hostcomputer 1430 may be used in certain embodiments, for example, toprovide remote patient monitoring.

In one embodiment, the system 1400 allows a clinician to select datacorresponding to one or more of the leads for display. The system 1400then automatically monitors and displays the selected data on at leastone of the display devices 1416, 1432. In certain embodiments, the audiocomponent 1418 provides an audible alarm and/or verbal annunciation ofST-segment deviations that exceed a defined threshold. The interfacecomponent 1420 may include, for example, an integrated keypad, touchscreen, or other user controls. The interface component 1420 may alsoinclude, for example, interfaces for an external keyboard, a mouse, aprinter, an external storage device, and/or a network adapter.

It will be understood by those having skill in the art that many changesmay be made to the details of the above-described embodiments withoutdeparting from the underlying principles of the invention. The scope ofthe present invention should, therefore, be determined only by thefollowing claims.

1. A method for monitoring a patient and graphically representingST-segment deviations, the method comprising: acquiringelectrocardiogram (ECG) signals from a plurality of leads, each ECGsignal including a sequence of ST-segments between a QRS complex and a Twave; determining a baseline ST-segment deviation from an isoelectricvalue for each of the plurality of leads; determining a currentST-segment deviation from the isoelectric value for each of theplurality of leads; displaying a graph comprising: a first linear axisrepresenting ST-segment deviation values; and a second linear axisrepresenting the plurality of leads, wherein each of the plurality ofleads is associated with a respective location along the second linearaxis; displaying a first set of bar graphs representing the baselineST-segment deviations, wherein each first bar graph is displayed withrespect to one of the locations corresponding to a respective lead andis aligned relative to the first linear axis based on the baselineST-segment deviation for the respective lead; and displaying a secondset of bar graphs representing the current ST-segment deviations,wherein each second bar graph is displayed with respect to one of thelocations corresponding to a respective lead and is aligned relative tothe first linear axis based on the current ST-segment deviation for therespective lead; wherein each second bar graph has a width in thedirection of the second linear axis that is narrower than a width in thedirection of the second linear axis of the corresponding first bar graphfor a respective lead; wherein each second bar graph has an origin withrespect to the first axis at the baseline ST-segment deviation for arespective lead and extends along the first axis in a positive ornegative direction depending on whether the current ST-segment deviationis respectively greater or less than the baseline ST-segment deviation;and wherein, if the current ST-segment deviation is positive and is lessthan the baseline ST-segment deviation for a particular lead, the secondbar graph for the particular lead extends in the negative direction intothe corresponding first bar graph.
 2. The method of claim 1, whereindisplaying each first bar graph comprises: displaying the first bargraph between a first value relative to the first linear axis and asecond value relative to the first linear axis, wherein the first valuecorresponds to the isoelectric value, and wherein the second valuecorresponds to the baseline ST-segment deviation for the respectivelead.
 3. The method of claim 2, wherein displaying each second bar graphcomprises: displaying the second bar graph between the second valuerelative to the first linear axis and a third value relative to thefirst linear axis, wherein the third value corresponds to the currentST-segment deviation for the respective lead.
 4. The method of claim 1,further comprising: highlighting, at each of the locations along thesecond linear axis, at least one of the first bar graph and the secondbar graph to visually distinguish the first bar graphs from the secondbar graphs.
 5. The method of claim 4, wherein the highlighting comprisesone or more graphical elements selected from the group comprisingshading and coloring.
 6. The method of claim 5, further comprising:displaying one or more threshold lines substantially parallel to thesecond linear axis, each threshold line representing a thresholdST-segment deviation value; determining that at least one of the secondbar graphs intersects one of the threshold lines; and in response to thedetermination, changing the highlighting of the at least one second bargraphs that intersects one of the threshold lines.
 7. The method ofclaim 1, wherein displaying the graph comprises: displaying a firstportion of the graph in a first window, the first portion correspondingto a first subset of leads; and displaying a second portion of the graphin a second window, the second portion corresponding to a second subsetof leads.
 8. The method of claim 7, wherein the first subset of leadsincludes limb leads and the second subset of leads includes precordialleads.
 9. A patient monitoring system for graphically representingST-segment deviation, the system comprising: a receiver to acquireelectrocardiogram (ECG) signals through a plurality of leads, the ECGsignals including an ST-segment between a QRS complex and a T wave; aprocessor to process the ECG signals to determine, for each of theplurality of leads, baseline ST-segment deviations from an isoelectricvalue and current ST-segment deviations from the isoelectric value; adisplay device for displaying a user interface; and a display module fordisplaying a graph in the user interface, the graph comprising: a firstlinear axis representing ST-segment deviation values; and a secondlinear axis representing the plurality of leads, wherein each of theplurality of leads is associated with a respective location along thesecond linear axis; wherein the display module displays a first set ofbar graphs representing the baseline ST-segment deviations, each firstbar graph being displayed with respect to one of the locationscorresponding to a respective lead and being aligned relative to thefirst linear axis based on the baseline ST-segment deviation for therespective lead; and wherein the display module displays a second set ofgraphic indicia representing the current ST-segment deviations, eachsecond bar graph being displayed with respect to one of the locationscorresponding to a respective lead and being aligned relative to thefirst linear axis based on the current ST-segment deviation for therespective lead; wherein each second bar graph has a width in thedirection of the second linear axis that is narrower than a width in thedirection of the second linear axis of the corresponding first bar graphfor a respective lead; wherein each second bar graph has an origin withrespect to the first axis at the baseline ST-segment deviation for arespective lead and extends along the first axis in a positive ornegative direction depending on whether the current ST-segment deviationis respectively greater or less than the baseline ST-segment deviation;and wherein, if the current ST-segment deviation is positive and is lessthan the baseline ST-segment deviation for a particular lead, the secondbar graph for the particular lead extends in the negative direction intothe corresponding first bar graph.
 10. The system of claim 9 wherein thedisplay module is further configured to: display the first bar graphbetween a first value relative to the first linear axis and a secondvalue relative to the first linear axis, wherein the first valuecorresponds to the isoelectric value, and wherein the second valuecorresponds to the baseline ST-segment deviation for the respectivelead; and display the second bar graph between the second value relativeto the first linear axis and a third value relative to the first linearaxis, wherein the third value corresponds to the current ST-segmentdeviation for the respective lead.
 11. The system of claim 9 wherein thedisplay module is further configured to: highlight, at each of thelocations along the second linear axis, at least one of the first bargraph and the second bar graph to visually distinguish the first bargraphs from the second bar graphs.
 12. The system of claim 11, whereinthe highlighting comprises one or more graphical elements selected fromthe group comprising shading and coloring.
 13. The system of claim 12,wherein the display module is further configured to: display one or morethreshold lines substantially parallel to the second linear axis, eachthreshold line representing a threshold ST-segment deviation value;determine that at least one of the second bar graphs intersects one ofthe threshold lines; and in response to the determination, change thehighlighting of the at least one second bar graphs that intersects oneof the threshold lines.
 14. The system of claim 9, wherein the displaymodule is further configured to: display a first portion of the graph ina first window, the first portion corresponding to a first subset ofleads; and display a second portion of the graph in a second window, thesecond portion corresponding to a second subset of leads.
 15. The systemof claim 14, wherein the first subset of leads includes limb leads andthe second subset of leads includes precordial leads.
 16. A patientmonitoring system for graphically representing ST-segment deviation, thesystem comprising: means for acquiring electrocardiogram (ECG) signalsthrough a plurality of leads, the ECG signals including an ST-segmentbetween a QRS complex and a T wave; means for processing the ECG signalsto determine, for each of the plurality of leads, baseline ST-segmentdeviations from an isoelectric value and current ST-segment deviationsfrom the isoelectric value; means for displaying a user interface; andmeans for displaying a graph in the user interface, the graphcomprising: a first linear axis representing ST-segment deviationvalues; and a second linear axis representing the plurality of leads,wherein each of the plurality of leads is associated with a respectivelocation along the second linear axis; wherein the means for displayingdisplays a first set of bar graphs representing the baseline ST-segmentdeviations, each first bar graph being displayed with respect to one ofthe locations corresponding to a respective lead and being alignedrelative to the first linear axis based on the baseline ST-segmentdeviation for the respective lead; and wherein the means for displayingdisplays a second set of bar graphs representing the current ST-segmentdeviations, each second bar graph being displayed with respect to one ofthe locations corresponding to a respective lead and being alignedrelative to the first linear axis based on the current ST-segmentdeviation for the respective lead; wherein each second bar graph has awidth in the direction of the second linear axis that is narrower than awidth in the direction of the second linear axis of the correspondingfirst bar graph for a respective lead; wherein each second bar graph hasan origin with respect to the first axis at the baseline ST-segmentdeviation for a respective lead and extends along the first axis in apositive or negative direction depending on whether the currentST-segment deviation is respectively greater or less than the baselineST-segment deviation; and wherein, if the current ST-segment deviationis positive and is less than the baseline ST-segment deviation for aparticular lead, the second bar graph for the particular lead extends inthe negative direction into the corresponding first bar graph.